Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@server/src/modules/kobo/services/kobo-sync.service.ts`:
- Around line 438-441: The smart-scope matching logic in getDelta is being
queried repeatedly within the same sync request, causing unnecessary DB round
trips. Compute getSyncedSmartScopeMatches once per request using the existing
userId and accessibleLibraryIds, then pass or reuse that cached result in
buildEligibleBooksWhereClause, fetchEligibleSnapshotRows,
fetchEligibleBooksByIds, and buildTagItems instead of recomputing it. If
threading the value through is too invasive, add request-scoped memoization
keyed by (userId, accessibleLibraryIds) inside KoboSyncService.
- Around line 471-495: The getSyncedSmartScopeMatches method is issuing one
awaited db.select() per SmartScope inside the for...of loop, creating sequential
N+1 queries on the sync path. Refactor this so the per-scope book lookups run
independently in parallel, e.g. by building the queries from each scope’s filter
and resolving them together before populating the Map. Keep the existing
behavior for scopes without a filter and preserve the same return shape from
getSyncedSmartScopeMatches.
- Around line 471-495: The special-case in getSyncedSmartScopeMatches is wrong
for SmartScopes with no filter, because it forces an empty match list instead of
using the existing BookQueryBuilder.buildWhere behavior that returns all
accessible books. Remove the !scope.filter branch and always build the where
clause for each scope so no-filter scopes sync the full accessible set. Make
sure the change preserves the existing accessibleLibraryIds/userId inputs and
also covers the eligibility path that reuses getSyncedSmartScopeMatches.

---

Nitpick comments:
In `@client/src/features/smart-scope/components/SmartScopeEditorPanel.vue`:
- Around line 204-214: Add switch semantics to the custom toggle in
SmartScopeEditorPanel so assistive tech can announce its state: update the
existing toggle button that flips draftSyncToKobo to expose it as a switch with
a bound checked state. Keep the current click behavior, but add the appropriate
ARIA role and state binding on the button element so screen readers report
on/off instead of a generic button.

In `@server/src/modules/kobo/services/kobo-sync.service.ts`:
- Around line 471-495: The SmartScope lookup in getSyncedSmartScopeMatches uses
the fetched SmartScope object itself as the Map key, which depends on reference
identity and is fragile. Update getSyncedSmartScopeMatches in
kobo-sync.service.ts to key the result by a stable identifier such as scope.id,
or store the scope alongside the book IDs in the Map value, and then adjust the
caller that consumes this map to use that identifier instead of the object
reference.

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@server/src/modules/kobo/services/kobo-sync.service.ts`:
- Around line 719-722: The smart-scope membership filter in kobo-sync.service.ts
is flattening all matched book IDs into a large inArray(...) bind list, which
can explode parameter counts on the request path. Update the logic around
getSyncedSmartScopeMatchesCached and membershipFilter to avoid materializing all
smartScopeBookIds; instead build SQL/EXISTS-based OR predicates like the
collection branch, or chunk the IDs before combining them if reuse is needed.